JP4202505B2 - Vapor compression refrigeration cycle - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a vapor compression refrigeration cycle that is suitably used as an air conditioner for automobiles, business use, or home use.
[0002]
[Prior art]
In today's world where it is demanded globally to prevent global warming due to chlorofluorocarbons, in the field of vapor compression refrigeration cycles where chlorofluorocarbons have been used as refrigerants, carbon dioxide, for example, is one of the countermeasures against defluorocarbons. A vapor compression refrigeration cycle using (CO ₂ ) (hereinafter abbreviated as CO ₂ cycle) has been proposed.
[0003]
In such a CO ₂ cycle, since the coefficient of performance (COP) of the refrigeration cycle is worse than that using chlorofluorocarbon, it is required to improve this.
[0004]
As a method for improving the COP of the CO ₂ cycle, for example, it has been generally performed to perform heat exchange of the refrigerant using an internal heat exchanger, for example. Here, FIG. 6 shows a CO ₂ cycle circuit using an internal heat exchanger. The vapor compression refrigeration cycle 101 (hereinafter simply referred to as the refrigeration cycle 101) includes a gas-liquid separator 102 that stores refrigerant CO ₂ and a compressor that compresses the gas-phase refrigerant from the gas-liquid separator 102. 103 and a radiator (gas cooler) 104 that cools the refrigerant compressed by the compressor 103 by exchanging heat with the outside air, and the refrigerant from the gas cooler 104 is evaporated and supplied to the compressor 102. The pressure of the refrigerant from the gas cooler 104 disposed in the rear stage of the evaporator 108, the internal heat exchanger 105 that performs heat exchange between the refrigerant at the outlet of the gas cooler 104 and the refrigerant at the outlet of the evaporator 108, and the internal heat exchanger 105 a high pressure control valve 106 for controlling the evaporator 10 from the gas cooler 104 as the degree of superheat of the refrigerant CO ₂ in disposed downstream compressor 103 inlet side becomes a predetermined value of the high pressure control valve 106 The superheat degree control valve 107 that adjusts the flow rate of the refrigerant to 8 constitutes a basic circuit.
[0005]
In this refrigeration cycle 101, as shown in FIG. 6, the gas-liquid separator 102 and the compressor 103 are connected to the pipe _P101 , the compressor 103 and the gas cooler 104 are connected to the pipe _P102 , and the gas cooler 104 and the internal heat exchanger are exchanged. in vessel 105 and the piping P _103, in the internal heat exchanger 105 and the high-pressure control valve 106 and piping P _104, the high pressure control valve 106 in the superheat degree control valve 107 and piping P _105, a superheat control valve 107 evaporated The evaporator 108 is connected to the pipe P ₁₀₆ , the evaporator 108 and the internal heat exchanger 105 are connected to the pipe P ₁₀₇ , and the internal heat exchanger 105 and the gas-liquid separator 102 are connected to the pipe P ₁₀₈ .
[0006]
In such a refrigeration cycle 101, carbon dioxide (CO ₂ ), which is a refrigerant supplied from the gas-liquid separator 102, is compressed by the compressor 103 to a pressure equal to or higher than its critical pressure, and this CO ₂ is discharged through the pipe _P102 . And then flows into the gas cooler 104 through the internal heat exchanger 105, the high-pressure control valve 106, the superheat control valve 107, the evaporator 108, the internal heat exchanger 105, the gas-liquid separator 102, and the compressor 103. Circulate.
[0007]
Thereby, in the refrigeration cycle 101, the relatively high temperature (for example, about 40 to 50 degrees) of CO ₂ flowing out from the gas cooler 104 and the relatively low temperature (for example, 5 to 10) flowing out of the evaporator 108 by the internal heat exchanger 105. Heat exchange is performed with CO _{2 at the} degree, and the temperature of CO ₂ from the outlet of the evaporator 108 rises and is returned to the gas-liquid separator 102. In the refrigeration cycle 101, the COP is improved in order to cool the refrigerant at the outlet of the gas cooler 104 in proportion to the amount of temperature exchanged by the internal heat exchanger 105.
[0008]
Here, in the refrigeration cycle 101, in order to control the degree of superheating of the CO ₂ when sucked by the compressor 103, a temperature detection means such as a temperature sensing cylinder (not shown) is attached to the pipe P ₁₀₇ at the outlet of the evaporator 108, The refrigerant temperature at the outlet of the evaporator 108 is detected by this temperature detecting means, and the opening / closing control of the superheat degree control valve 107 is performed according to the detected temperature.
[0009]
[Problems to be solved by the invention]
FIG. 7 shows the relationship between the outside air temperature, the COP improvement rate (%), and the discharge temperature of the compressor 103 in the refrigeration cycle 101 when the internal heat exchanger 105 is used.
[0010]
As is clear from FIG. 7, in the refrigeration cycle 101, when the outside air temperature is low, there is little effect of COP improvement when the internal heat exchanger 105 is used, and from the time when the outside air temperature exceeds a certain level, The COP improvement rate increases in proportion to the outside air temperature.
[0011]
However, in the CO ₂ refrigeration cycle 101 using the internal heat exchanger 105, the suction steam of the compressor 103 is overheated, and accordingly, the discharge temperature of the compressor 103 rises excessively, and the inside of the compressor 103 There was a problem that the oil (lubricating oil) deteriorated. Specifically, in the refrigeration cycle 101, when the discharge refrigerant temperature of the compressor 103 exceeds approximately 150 degrees, the properties of the lubricating oil begin to be affected. However, by using the internal heat exchanger 105, the discharge The temperature rose to 150 to 180 degrees, and there was a problem that the life of the lubricating oil was remarkably shortened.
[0012]
The present invention has been proposed in view of such a situation, and is a vapor compression refrigeration cycle capable of improving COP while suppressing deterioration of the refrigerant discharge temperature and preventing deterioration of the lubricating oil. The purpose is to provide.
[0013]
[Means for Solving the Problems]
The vapor compression refrigeration cycle according to the present invention that has solved the above problems uses a carbon dioxide (CO ₂ ) refrigerant as a refrigerant, compresses the gas-phase refrigerant, and exchanges heat between the refrigerant compressed by the compressor and an external fluid. A radiator that cools and cools, an evaporator that evaporates the refrigerant from the radiator and supplies it to the compressor, an internal heat exchanger that exchanges heat between the refrigerant at the radiator outlet and the refrigerant at the evaporator outlet, First refrigerant temperature detection means for detecting the refrigerant temperature from the evaporator supplied to the internal heat exchanger, and second refrigerant temperature detection means for detecting the refrigerant temperature from the evaporator outlet flowing out from the internal heat exchanger A switching selection means for switching and selecting one of a refrigerant temperature detection value from the first refrigerant temperature detection means and a refrigerant temperature detection value from the second refrigerant temperature detection means under a predetermined condition, and an internal heat exchanger It is attached to the flow path on the outlet side and -Option was based on the refrigerant temperature detection value, the degree of superheat of the refrigerant in the compressor inlet side and a superheat control valve for adjusting the flow rate of refrigerant flowing into the evaporator to a predetermined value.
[0014]
In the vapor compression refrigeration cycle, the switching selection means switches and selects either the refrigerant temperature detection value from the first refrigerant temperature detection means or the refrigerant temperature detection value from the second refrigerant temperature detection means under a predetermined condition. Based on the selected refrigerant temperature detection value, the superheat degree control valve adjusts the flow rate of the refrigerant flowing into the evaporator so that the superheat degree of the refrigerant on the compressor inlet side becomes a predetermined value.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described with reference to the drawings. The present invention vapor compression refrigeration cycle 1 shown in FIG. 1 according to the (hereinafter, simply referred to as refrigeration cycle 1.) Is the air-conditioning system mounted e.g. on a vehicle such as a passenger car, carbon dioxide (CO ₂₎ As a refrigerant, a gas-liquid separator 2 that separates and stores the refrigerant into a liquid phase state and a gas phase state, a compressor 3 that compresses the refrigerant in the gas phase state from the gas liquid separator 2, and the compressor 3 A radiator (gas cooler) 4 connected to the latter stage, an evaporator 8 that evaporates the refrigerant from the gas cooler 4 and supplies it to the compressor 3, a refrigerant at the outlet of the gas cooler 4, and a refrigerant at the outlet of the evaporator 8 The internal heat exchanger 5 is configured to perform heat exchange with the internal heat exchanger 5, and is disposed downstream of the internal heat exchanger 5, and is disposed downstream of the high pressure control valve 6 that controls the pressure of the refrigerant from the gas cooler 4. Evaporate so that the degree of superheat of the refrigerant at the inlet side of the compressor 2 becomes a predetermined value Basic circuit is constituted by the superheat control valve 7 for adjusting the flow rate of refrigerant flowing into 8.
[0016]
In this refrigeration cycle 1, as shown in FIG. 1, the gas-liquid separator 2 and the compressor 3 are connected to the pipe P ₁ , the compressor 3 and the gas cooler 4 are connected to the pipe P ₂ , and the gas cooler 4 and the internal heat exchange. in vessel 5 and the piping P _3, in the internal heat exchanger 5 and the high-pressure control valve 6 and the piping P _4, a high pressure control valve 6 in superheat control valve 7 and the pipe P _5, a superheat control valve 7 evaporation The evaporator 8 is connected to the pipe P ₆ , the evaporator 8 and the internal heat exchanger 5 are connected to the pipe P ₇ , and the internal heat exchanger 5 and the gas-liquid separator 2 are connected to the pipe P ₈ .
[0017]
Further, the refrigerating cycle 1 is arranged on the evaporator 8 outlet pipe P _7, a first refrigerant temperature detecting means 9 for detecting the temperature of the refrigerant flowing out of the evaporator 8, distribution on the pipe P ₈ The second refrigerant temperature detecting means 10 for detecting the temperature of the refrigerant flowing out of the evaporator 8 at the position of the outlet of the internal heat exchanger 5, and the refrigerant temperature detection value from the first refrigerant temperature detecting means 9 A switching control unit 11 is provided that switches and selects one of the refrigerant temperature detection values from the second refrigerant temperature detection means 10 under a predetermined condition and outputs the selected value to the superheat degree control valve 7 as a detection signal.
[0018]
The gas-liquid separator 2 supplies the refrigerant CO ₂ in a gas phase state to the compressor 3, and converts the CO ₂ from the evaporator 8 flowing in via the internal heat exchanger 5 into the gas-phase CO ₂ and the gas. Separated and stored in phase CO ₂ .
[0019]
The compressor 3 compresses and discharges CO ₂ in a gas phase state from the gas-liquid separator 2 to a critical pressure or higher.
[0020]
The gas cooler 4 cools CO ₂ compressed to a critical pressure or higher by the compressor 3 by exchanging heat with an external fluid such as outside air.
[0021]
Internal heat exchanger 5 exchanges heat with the CO ₂ flowing out of the CO ₂ and the evaporator 8 flowing out of the gas cooler 4.
[0022]
High-pressure control valve 6, the CO ₂ from the gas cooler 4 which has passed through the internal heat exchanger 5 as well as vacuum, internal heat in accordance with the temperature of CO ₂ on the outlet side of the internal heat exchanger 5 (the pipe P ₄ side) The pressure on the outlet side of the exchanger 5 is controlled.
[0023]
The superheat degree control valve 7 adjusts the flow rate of CO ₂ flowing into the evaporator 8 so that the superheat degree of the suction of CO ₂ on the inlet side of the compressor 3 becomes a predetermined value. In this embodiment, the superheat degree control valve 7 has a configuration using an electromagnetic valve, and CO ₂ at the inlet side of the compressor 3 based on a detection signal output from a switching control unit 11 described later in detail. The solenoid valve is opened and closed so that the degree of superheat of the intake becomes 0 to 50 degrees (deg).
[0024]
Here, the superheat degree control valve 7 has a detected temperature from either the first refrigerant temperature detecting means 9 or the second refrigerant temperature detecting means 10 input via the switching control section 11 and the evaporation temperature of CO ₂ . + Control is performed to adjust the opening of the solenoid valve so that the temperature corresponds to the degree of superheat. Specifically, since the CO ₂ evaporation temperature is approximately 0 degrees and the superheat setting is 0 to 50 degrees as described above, the first refrigerant temperature detecting means 9 or the second refrigerant temperature detecting means 10 to 0. It suffices to obtain a temperature detection value of 50 degrees to 50 degrees. Therefore, the superheat degree control valve 7 is set so that the detected temperature from the first refrigerant temperature detecting means 9 or the second refrigerant temperature detecting means 10 input via the switching control unit 11 is 0 degrees to 50 degrees. The opening degree of the solenoid valve is adjusted.
[0025]
In this embodiment, the first refrigerant temperature detection means 9 and the second refrigerant temperature detection means 10 are each configured by using a thermistor (hereinafter referred to as the thermistor 9 and the thermistor 10 as appropriate). Detects the refrigerant temperature in the pipe P _{7 at the} outlet of the evaporator 8 and outputs a detection signal to the switching control unit 11. The thermistor 10 detects the refrigerant temperature in the pipe P _{8 at the} outlet of the internal heat exchanger 5 and outputs the detection signal. The data is output to the switching control unit 11.
[0026]
As shown in FIG. 1, the switching control unit 11 includes a sensor unit 12, a control unit 13, and a changeover switch 14, and selects one of the detection signals from the thermistor 9 and the thermistor 10 to overheat. This is output to the degree control valve 7. Here, the sensor unit 12 detects the temperature of the outside air and supplies data of the detected value to the control unit 13. And the control part 13 monitors the detected value data about the outside temperature supplied from the sensor part 12, and when the said outside temperature exceeds predetermined temperature, it outputs a switching control signal to the changeover switch 14.
[0027]
The change-over switch 14 detects either one by switching the connection of the switch S to either the terminal 14a to which the detection signal from the thermistor 9 is supplied or the terminal 14b to which the detection signal from the thermistor 10 is supplied. A signal is supplied to the superheat degree control valve 7.
[0028]
In the refrigeration cycle 1 having such a configuration, the refrigerant CO ₂ is compressed to a pressure equal to or higher than the critical pressure by the compressor 3 and discharged at a temperature of 100 degrees or more. This CO ₂ flows into the gas cooler 4 via the pipe P ₂ , and thereafter, the internal heat exchanger 5, the high pressure control valve 6, the superheat degree control valve 7, the evaporator 8, the internal heat exchanger 5, the air It circulates in order of the liquid separator 2 and the compressor 3. Here, the refrigerant CO ₂ is cooled to, for example, about 40 to 50 degrees by exchanging heat with the outside air in the gas cooler 4, and the pressure and flow rate are controlled by the high pressure control valve 6 and the superheat degree control valve 7. It becomes a liquid phase state of about 5 degrees and flows into the evaporator 8. Then, the refrigerant CO ₂ evaporates in the evaporator 8, and at this time, the interior of the vehicle is cooled by removing heat from the fluid around the evaporator 8. Further, in the refrigeration cycle 1, the internal heat exchanger 5, heat exchange is performed at a relatively temperatures and high CO ₂ from a relatively low temperature CO ₂ gas cooler 4 from the evaporator 8. By this heat exchange, in the refrigeration cycle 1, the refrigerant temperature rises and the refrigerant CO ₂ flows into the gas-liquid separator 2. In the gas-liquid separator 2, the CO ₂ from the evaporator 8 heat-exchanged by the internal heat exchanger 5 is separated into a liquid layer CO ₂ and a gas phase CO ₂ and stored.
[0029]
In the refrigeration cycle 1 such circulation of refrigerant CO ₂ is performed, the refrigerant CO ₂ from the evaporator 8 outlet is supplied to the temperature rise in the compressor 2 in the internal heat exchanger 5, the refrigerant in the pipe P ₇ The detected temperature of the thermistor 10 that detects the refrigerant temperature in the pipe P ₈ is always higher than the detected temperature of the thermistor 9 that detects the temperature. In the refrigeration cycle 1, the COP is improved in order to cool the refrigerant at the outlet of the gas cooler 4 in proportion to the amount of temperature exchanged by the internal heat exchanger 5.
[0030]
Hereinafter, control of the refrigeration cycle 1 will be described. At the start of the refrigeration cycle 1, the control unit 13 of the switching control unit 11 performs a compressor operation when the outside air temperature rises to a predetermined value (for example, 30 degrees) based on the detected value data of the outside air temperature from the sensor unit 12. 3 is controlled so as to reduce the degree of superheat (SH) of the refrigerant CO ₂ when sucked. Specifically, the control unit 13 detects the refrigerant temperature at the outlet of the evaporator 8 using the thermistor 9 when the outside air temperature is 30 degrees or less, and detects the internal heat using the thermistor 10 when the outside air temperature exceeds 30 degrees. Control is performed to detect the refrigerant temperature at the outlet of the exchanger 5. Thus, in the refrigeration cycle 1, when the outside air temperature is 30 degrees or less, the opening and closing of the solenoid valve in the superheat degree control valve 7 is adjusted based on the detected value of the thermistor 9 that detects the refrigerant temperature at the outlet of the evaporator 8. When the outside air temperature exceeds 30 degrees, the opening and closing of the solenoid valve of the superheat degree control valve 7 is adjusted based on the detected value of the thermistor 10 that detects the refrigerant temperature at the outlet of the internal heat exchanger 5.
[0031]
Regarding the opening and closing of the solenoid valve by the superheat degree control valve 7, when the value of the superheat degree is higher than a predetermined value, the opening degree of the solenoid valve is increased (opened). When the value is lower than the predetermined value, the opening degree of the electromagnetic valve may be reduced (closed). That is, by increasing the opening of the solenoid valve, in the refrigeration cycle 1, the amount of refrigerant flowing through the evaporator 8 and the internal heat exchanger 5 is increased, and the detection values of the thermistors 9 and 10 are decreased. On the other hand, when the opening degree of the solenoid valve is reduced, the amount of refrigerant flowing through the evaporator 8 and the internal heat exchanger 5 is reduced, and the detection values of the thermistors 9 and 10 are increased.
[0032]
The state of the refrigeration cycle 1 when the opening degree adjustment of the solenoid valve of the superheat degree control valve 7 is performed based on the refrigerant temperature detection value from the thermistor 9 as the first refrigerant temperature detection means will be described. In this case, the refrigerant CO ₂ is depressurized by the superheat degree control valve 7 and has a temperature of about 0 ° C., and the temperature is increased by taking heat from the surrounding fluid by the evaporator 8. Here, the superheat degree control valve 7 adjusts the opening degree of the solenoid valve so that the detected temperature of the thermistor 9 attached to the pipe P ₇ at the outlet of the evaporator 8 becomes a temperature corresponding to the evaporation temperature + superheat degree. . Specifically, in this case, assuming that the evaporation temperature is 0 degree and the superheat degree is set to 0 to 50 degrees, the temperature to be detected from the thermistor 9 is 0 degrees to 50 degrees. Therefore, the superheat degree control valve 7 adjusts the opening degree of the valve so that the detected temperature of the thermistor 9 attached to the pipe P ₇ at the outlet of the evaporator 8 becomes 0 to 50 degrees. In this case, the detected temperature of the thermistor 10 which is the second refrigerant temperature detecting means is about 20 to 30 degrees, and excess refrigerant CO ₂ is accumulated in the gas-liquid separator 2. Become.
[0033]
Next, the state of the refrigeration cycle 1 when the opening degree adjustment of the solenoid valve of the superheat degree control valve 7 is switched so as to be performed based on the refrigerant temperature detection value from the thermistor 10 as the second refrigerant temperature detection means. Will be described. Also in this case, the superheat degree control valve 7 adjusts the opening degree of the electromagnetic valve so that the detected temperature of the thermistor 10 becomes a temperature corresponding to the evaporation temperature + superheat degree. Therefore, the superheat degree control valve 7 adjusts the opening degree of the valve so that the refrigerant temperature at the outlet of the internal heat exchanger 5 detected by the thermistor 10 becomes 0 to 50 degrees. Here, since the temperature detected by the thermistor 10 is always higher than the temperature detected by the thermistor 9, the superheat control valve 7 opens the solenoid valve so as to relatively lower the refrigerant temperature at the outlet of the internal heat exchanger 5. It controls to increase the amount of refrigerant CO ₂ circulating in the circuit. As a result, in the refrigeration cycle 1, the degree of superheat of the refrigerant sucked into the compressor 3 decreases. In this case, since a large amount of refrigerant CO ₂ having a high density flows in the circuit, there is almost no excess refrigerant CO ₂ in the gas-liquid separator 2.
[0034]
By performing such control, in this refrigeration cycle 1, as shown in FIG. 2, the refrigerant discharge temperature of the compressor 3 is about 100 to 120 degrees even when the outside air temperature rises and exceeds 30 degrees. As a result, the COP can be improved while suppressing the discharge temperature of the compressor 3 and preventing the deterioration of oil (lubricating oil).
[0035]
Next, another embodiment of the refrigeration cycle will be described with reference to FIG. In addition, the same code | symbol is attached | subjected to the part same as the refrigerating cycle 1 of FIG. 1, and the description is abbreviate | omitted. The refrigeration cycle 1A shown in FIG. 3 has the same basic circuit configuration as the refrigeration cycle 1 described above, and uses temperature sensing tubes as the first refrigerant temperature detection means 9A and the second refrigerant temperature detection means 10A. (Hereinafter, referred to as a temperature sensing cylinder 9A and a temperature sensing cylinder 10A), the pressure-type configuration is used for opening / closing control of the superheat degree control valve. That is, the temperature sensing cylinder 9A and the temperature sensing cylinder 10A of the refrigeration cycle 1A are filled with fluid at a predetermined density, and the refrigerant temperature detection value is transferred to the switching control unit 11A by the pressure of the fluid (hereinafter referred to as detection pressure). It is designed to output.
[0036]
Further, in the refrigeration cycle 1A, a switching control unit 11A is configured using a switching valve 15 instead of the switching switch 14, and the switching valve 15 is based on a switching control signal from the control unit 13A. And the detected pressure of either of the temperature sensing cylinders 10A is switched and selected and supplied to the superheat degree control valve 7A. Furthermore, the superheat degree control valve 7A in the refrigeration cycle 1A is a mechanical type that adjusts the opening degree of the valve in accordance with the detected pressure supplied from the switching control unit 11A.
[0037]
Then, by performing the same setting and control as in the case of the refrigeration cycle 1 in FIG. 1, also in the refrigeration cycle 1A, as in the above-described refrigeration cycle 1, even when the outside air temperature rises and exceeds 30 degrees. The refrigerant discharge temperature of the compressor 3 can be suppressed to about 100 to 150 degrees, and the COP can be improved while preventing the deterioration of the oil (lubricating oil) of the compressor 3.
[0038]
Another embodiment of the refrigeration cycle will be described with reference to FIG. In addition, the same code | symbol is attached | subjected to the part same as the refrigerating cycle 1 of FIG. 1, and the description is abbreviate | omitted. The refrigeration cycle 1B shown in FIG. 4 has the same basic circuit configuration as the refrigeration cycle 1 described above, but a third refrigerant temperature detecting means for detecting the refrigerant temperature discharged from the compressor 3 for the switching control unit 11B. sensor portion 12A of the attached to the pipe P _2, on the basis of the detection value of the sensor unit 12A, the control unit 13B has a configuration for switching a detection signal supplied to the superheat control valve 7.
[0039]
In the refrigeration cycle 1B, in the initial state at the start of operation, as shown in FIG. 4, a detection signal from the thermistor 9 as the first refrigerant temperature detecting means is supplied to the superheat degree control valve 7. . Then, when the discharge refrigerant temperature of the compressor 3 rises and exceeds a predetermined temperature, the switching control unit 11B supplies a detection signal from the thermistor 10 as the second refrigerant temperature detection means to the superheat degree control valve 7. The switching control is performed.
[0040]
Specifically, in the switching control unit 11B, the control unit 13 monitors the detected value data about the discharge refrigerant temperature of the compressor 3 supplied from the sensor unit 12A, and the compressor 3 detected by the sensor unit 12A. When the value of the discharged refrigerant temperature reaches 120 degrees, which starts to affect the properties of the lubricating oil, a control signal is output to the changeover switch 14 and control for switching the connection of the switch S from the terminals 14a to 14b is performed. Do.
[0041]
By performing such control, in the refrigeration cycle 1B, when the discharge temperature of the compressor 3 exceeds a certain value, the superheat degree of the suction decreases, so that the discharge temperature of the compressor 3 is suppressed and the oil (lubricant oil) ) COP can be improved while preventing deterioration.
[0042]
In the refrigeration cycle 1B, the thermistor is used as the first refrigerant temperature detection means 9 and the second refrigerant temperature detection means 10 and the solenoid valve is used as the superheat degree control valve 7, as in the refrigeration cycle 1 of FIG. Furthermore, although it is configured by the electric switch 14, it is needless to say that these can be configured by a pressure type as in the refrigeration cycle 1A of FIG.
[0043]
Furthermore, in the above-described embodiment, the circuit is configured using the gas-liquid separator. However, as shown in FIG. 5, for example, the present invention can also configure the circuit without using the gas-liquid separator. . In FIG. 5, the same parts as those in the above-described embodiment are denoted by the same reference numerals. In the refrigeration cycle 1C shown in FIG. 5, the refrigerant flowing out of the evaporator 8 is supplied to the compressor 3 without going through the gas-liquid separator. On the other hand, in the refrigeration cycle 1 </ b> C, a surge tank 16 is disposed between the high-pressure control valve 6 and the superheat degree control valve 7, and excess refrigerant is stored in the surge tank 16. Here, the surge tank 16 only needs to have a storage capacity of about 500 to 1000 ml. Also in the refrigeration cycle 1C having such a configuration, by performing the same control as described above, it is possible to improve the COP while suppressing the discharge temperature of the compressor 3 and preventing the deterioration of the lubricating oil.
[0044]
In the embodiment described above, the degree of superheat of the refrigerant sucked into the compressor 3 is switched according to the outside air temperature or the refrigerant discharge temperature of the compressor 3, but the present invention is limited to this. Instead, the degree of superheat of the refrigerant may be controlled according to other factors such as the vehicle air conditioning load.
[0045]
【The invention's effect】
As described above in detail, according to the present invention, the switching selection means selects either the refrigerant temperature detection value from the first refrigerant temperature detection means or the refrigerant temperature detection value from the second refrigerant temperature detection means. By switching and selecting under a predetermined condition, based on the selected refrigerant temperature detection value, the superheat degree control valve causes the superheat degree of the refrigerant at the compressor inlet side to become a predetermined value from the radiator to the evaporator. Therefore, it is possible to provide a vapor compression refrigeration cycle capable of improving the COP while preventing the deterioration of the lubricating oil by suppressing the increase in the refrigerant discharge temperature of the compressor. .
[Brief description of the drawings]
FIG. 1 is a circuit diagram showing a configuration of a vapor compression refrigeration cycle of the present invention.
FIG. 2 is a characteristic diagram showing the relationship between the outside air temperature, the COP improvement rate (%), and the compressor discharge temperature in the vapor compression refrigeration cycle.
FIG. 3 is a circuit diagram showing another embodiment of the vapor compression refrigeration cycle of the present invention.
FIG. 4 is a circuit diagram showing another embodiment of the vapor compression refrigeration cycle of the present invention.
FIG. 5 is a circuit diagram showing another embodiment of the vapor compression refrigeration cycle of the present invention.
FIG. 6 is a circuit diagram of a CO ₂ cycle using an internal heat exchanger.
FIG. 7 is a characteristic diagram showing the relationship between the outside air temperature, the COP improvement rate (%), and the discharge temperature of the compressor in a CO ₂ cycle using an internal heat exchanger.
[Explanation of symbols]
1, 1A, 1B, 1C Refrigeration cycle 2 Gas-liquid separator 3 Compressor 4 Radiator (gas cooler)
5 Internal heat exchanger 6 High pressure control valve 7, 7A Superheat control valve 8 Evaporator 9 First refrigerant temperature detection means 10 Second refrigerant temperature detection means 11, 11A, 11B Switching control part 12, 12A Sensor part 13, 13A, 13B Control unit 14 selector switch 15 selector valve 16 surge tank

Claims (5)

Using carbon dioxide (CO ₂ ) as a refrigerant,
A compressor for compressing the gas-phase refrigerant;
A radiator that cools the refrigerant compressed by the compressor by exchanging heat with an external fluid;
An evaporator that evaporates the refrigerant from the radiator and supplies the refrigerant to the compressor;
An internal heat exchanger that exchanges heat between the refrigerant at the radiator outlet and the refrigerant at the evaporator outlet;
First refrigerant temperature detection means for detecting refrigerant temperature from the evaporator supplied to the internal heat exchanger;
Second refrigerant temperature detection means for detecting the refrigerant temperature from the evaporator outlet flowing out of the internal heat exchanger;
Switching selection means for switching and selecting either of the refrigerant temperature detection value from the first refrigerant temperature detection means and the refrigerant temperature detection value from the second refrigerant temperature detection means under a predetermined condition;
Based on the refrigerant temperature detection value from any one of the refrigerant temperature detection means selected by the switching selection means, the superheat degree of the refrigerant at the compressor inlet side is attached to the flow path on the outlet side of the internal heat exchanger. A superheat degree control valve for adjusting the flow rate of the refrigerant flowing into the evaporator so as to be a predetermined value;
A vapor compression refrigeration cycle comprising: The first refrigerant temperature detection means and the second refrigerant temperature detection means are thermistors that output a refrigerant temperature detection value as an electrical signal,
The switch selection means switches the switch based on which electric signal from each thermistor is supplied to the superheat degree control valve, a temperature sensor for detecting the outside air temperature, and the detection value of the temperature sensor. 2. The vapor compression refrigeration cycle according to claim 1, further comprising changeover switch control means for performing switch changeover control. The first refrigerant temperature detection means and the second refrigerant temperature detection means are temperature-sensitive cylinders in which a fluid is sealed and a refrigerant temperature detection value is output by the pressure of the fluid,
The switching selection means is based on a switching valve that switches which fluid pressure from each temperature sensing cylinder is supplied to the superheat degree control valve, a temperature sensor that detects an outside air temperature, and a detection value of the temperature sensor. The vapor compression refrigeration cycle according to claim 1, further comprising switching valve control means for switching the switching valve. The first refrigerant temperature detection means and the second refrigerant temperature detection means are thermistors that output a refrigerant temperature detection value as an electrical signal,
The switching selection means includes a changeover switch for switching which electric signal from each thermistor is supplied to the superheat degree control valve, a third refrigerant temperature detection means for detecting the refrigerant discharge temperature of the compressor, The vapor compression refrigeration cycle according to claim 1, further comprising changeover switch control means for performing changeover control of the changeover switch based on a detection value of the third refrigerant temperature detection means. The first refrigerant temperature detection means and the second refrigerant temperature detection means are temperature-sensitive cylinders in which a fluid is sealed and a refrigerant temperature detection value is output by the pressure of the fluid,
The switching selection means includes a switching valve for switching which fluid pressure from each temperature sensing cylinder is supplied to the superheat degree control valve, and third refrigerant temperature detection means for detecting the discharge refrigerant temperature of the compressor. And a switching valve control means for switching the switching valve based on a detection value of the third refrigerant temperature detection means.

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